On Mon, 15 Mar 2010 12:55:11 +0100 Benjamin Tissoires <tisso...@cena.fr> said:
> >>> XI2 allows devices to change at runtime. Hence a device may add or remove > >>> valuators on-the-fly as touchpoints appear and disappear. There is a > >>> chance of a race condition here. If a driver decides to add/remove > >>> valuators together with the touchpoints, a client that skips events may > >>> miss out. e.g. if a DeviceChanged event that removes an axis is followed > >>> by one that adds an axis, a client may only take the second one as > >>> current, thus thinking the axis was never removed. There is nothing in > >>> the XI2 specs that prohibits this. Anyways, adding removing axes together > >>> with touchpoints seems superfluous if we use the presence of an axis as > >>> indicator for touch. Rather, I think a device should be set up with a > >>> fixed number of valuators describing the default maximum number of > >>> touchpoints. Additional ones can be added at runtime if necessary. > >> > >> agreed. i really see this having a fixed # of touch points - and not > >> changing - unless you literally unplug/plug in new hardware that has > >> different features (has more or less in the way of touch point support). > > We can have a fixed number of touch point but send only the required > ones. So agreed too. The point is: how many touch point do we have. The > kernel knows how many touches a device can send as the data are not > serialized. But after that, we have no idea of how many touches the > device support. > > With the mask system (or the packing of the touches at the beginning), > we will send only the right number of touches, but the description will > be very heavy. If each point has 5 axes (trackingID, x, y, width, height > for instance) we will have 50 valuators if we support 10 touches ;-) By > the way, it's not the point here. this is what i'm concerned about. there are touch surfaces that now support 10 touches - AND they can give you not just x,y but radius (x and y) too. so 10 touch points -> 40 valuators. already blown the 36 valuator limit - and we havent added yet more things like tracking id, separate pressure, angle etc. properties. multiple devices with valuators for these touch params will handle this. anyway - that's my concern for now. -- ------------- Codito, ergo sum - "I code, therefore I am" -------------- The Rasterman (Carsten Haitzler) ras...@rasterman.com _______________________________________________ xorg-devel@lists.x.org: X.Org development Archives: http://lists.x.org/archives/xorg-devel Info: http://lists.x.org/mailman/listinfo/xorg-devel